Web marking systems and methods

ABSTRACT

Apparatus for and a method of marking a web  10  advancing along a path includes a monitoring station  11  at which the web  10  is observed and including a signal generator arranged to produce an appropriate mark signal on detecting a location to be marked as well as the nature of the required mark. A tab applicator  20  is disposed downstream of the monitoring station for applying an adhesive tab  34  to the web in a timed relationship to the advancement of the web so as to adhere the tab  34  to the required location on the web. The tab applicator includes an online printer receiving a signal from the signal generator, whereby an applied tab may carry appropriate indicia for the location being marked.

This invention relates to a marking system for a web advancing along apath, and also to a method of marking such a web.

Many industrial processes employ stock materials in web form, the webbeing advanced along a path to allow the required processing. Forexample, in the printing industry, a web of paper may be supplied inroll form and the web is drawn from the roll as the paper printingprogresses, whereafter the web is cut into separate printed sheets. Inthe textile industry, many fabrics are manufactured in the form of anelongate web which is then spooled before being supplied to a garmentmanufacturer, for making up, or to a printer for the printing of asuitable design or pattern on to the fabric.

As manufactured, many webs of stock materials include defects. Thesedefects might include a splice undertaken at the time of manufacture, toallow continuous manufacturing processes to operate, defects in thewidth of the web or in the thickness of the material, or variations inquality along the length of the web. Depending upon the particular web,many other kinds of defect may be present, but which cannot be allowedto pass through to a finished product manufactured from the material ofthe web.

In order to eliminate the likelihood of such a defect passing through aprocessing stage to a finished product, it is known to observe the webas it is despooled, and then to mark an area which must be cut out, soas not to be used in a processing operation performed on the web,downstream of the observation station. Alternatively, aftermanufacturing a web or performing a conversion process on a web, the webmay be observed for defects as it is spooled or re-spooled. Typically, ahuman operator might watch the web and then apply to the web a simplepaper label which will be clearly visible in a subsequent process. Forexample, when the web is observed as it is about to be spooled orre-spooled, a brightly coloured label may be manually inserted into thespooling web to be left projecting from the side edge of the spooledweb, so that it is immediately apparent the web has been labelled.

A human operator can apply a selected colour of label, depending uponthe observed fault. For example, the operator can fairly easily have atleast three different colours of label and then apply the appropriatelabel for the defect observed. Such labels could be pre-printed to havesome wording indicative of the observed defect.

It is difficult for a human operator to concentrate for long periods,watching for defects in a web as it is despooled. As a consequence,equipment has been designed to look for certain kinds of defect and thento cause a label to be automatically applied to the web, by theequipment detecting the presence of a defect. For example, one proposaluses a conventional labelling machine to apply a self-adhesive label tothe advancing web, using conventional labelling technology, but adisadvantage of such equipment is that the machine must be pre-chargedwith a particular kind of label for use during an entire despooling orspooling operation. As a consequence, only one kind of label can beapplied, irrespective of the nature of the detected defect.

This invention aims at addressing the above problem, in order to allowthe use of equipment which can identify different kinds of defects in anadvancing web, and then appropriately to mark the web to indicate notjust where the defect is, but also what kind of defect is present.

According to one aspect of the present invention, there is provided amarking system for a web advancing along a path, comprising:

-   -   a monitoring station at which the web advancing along said path        is observed;    -   mark signal means arranged to produce an appropriate mark signal        on detection of a location to be marked and the nature of the        required mark;    -   a tab applicator disposed downstream of the monitoring station        and arranged to apply an adhesive tab to the web at the detected        location, the tab inserter including an on-line printer for        printing indicia on to each tab before the tab is applied to the        web; and    -   control means receiving the mark signal from the mark signal        means and driving the on-line printer and the tab applicator in        a timed relationship to the advancement of the web whereby each        tab is positioned at the detected location and carries        appropriate indicia for that location.

According to a second but closely related aspect of this invention,there is provided a method of marking a web advancing along a path,which method comprises:

-   -   monitoring the web as it passes through a monitoring station        provided on said path and producing a mark signal on detection        of a location on the web to be marked, the mark signal including        information about the nature of the required mark;    -   feeding the mark signal to control means which provides a drive        signal for an on-line printer and a tab applicator provided        downstream of the monitoring station, the drive signal being        provided in a timed relationship to the advancement of the web;        and    -   using the drive signal to print an adhesive tab with the on-line        printer so that the tab carries appropriate indicia for the        required mark and thereafter applying the tab to the web,        whereby each applied tab is positioned at the noted location and        carries appropriate indicia for that location.

With the marking system and method of this invention, it becomespossible to identify the nature of a defect noted as being present in anadvancing web. The defect is flagged up by attaching to the web anadhesive tab in the vicinity of the defect, but the tab is printedimmediately before application with suitable indicia in order toidentify the nature of the defect. This allows more effective operationof a process performed on the web downstream of the marking station, andpermits a decision to be made at some point subsequently as to whetherthe defect may be ignored, or whether that part of the web must beeliminated from the processing. A further possibility is for thebeginning and end points of a defect to be appropriately marked in theevent that there is an elongate section of the web which should beeliminated from the processing.

Preferably, the tab applicator includes a labelling head adapted toapply tabs to the web, each tab being in the form of a self-adhesivelabel. Such a labelling head may include at least one air-jet nozzleappropriately disposed to direct a jet of air on to a tab dischargedfrom the labelling head and so to apply that tab to the advancing web.By suitable adjustment of the timing, tabs may be applied transverselyto the direction of advancement of a web, even when the web has arelatively high linear speed of advancement. In this way, each tab maybe left projecting from the edge of the web. In this case, it ispreferred for each label to carry adhesive on only that part whichadheres to the web, the projecting part of the label being free ofadhesive, though for handling purposes a strip of adhesive may bepresent on that projecting part.

The in-line printer advantageously is arranged to allow the printing ofalphanumeric characters on to each tab. For example, by printing threeseparate characters, a very large number of different marks may begiven, or each mark may be in the form of a mnemonic for a particularkind of defect. Such a printer may comprise one of a dot-matrix printhead, a thermal transfer print head or even a direct thermal print headbut in the latter case each tab must be of a thermally-responsivematerial in order to allow the thermal print head to print markings onto the tab.

Preferably, the tab applicator is arranged to advance the next tab to beapplied initially at a low speed while printing takes place and then ata high speed and then to apply a printed tab to the advancing web, atthe required location. Such operation is controlled by the controlmeans, which responds to the mark signal produced by the monitoringmeans and also a further signal dependent upon the speed of advancementof the web such that the tab is applied to the appropriate part of theweb, at which is located the noted defect. That further signal maysimply be a fixed time interval calculated on the basis of a constantknown web speed and the distance between the monitoring station and thetab applicator. Alternatively, the web speed could be monitored and thefurther signal determined dependent upon the instantaneous web speed.

Monitoring means may be provided at the monitoring station, configuredto suit the defect or defects which are to be detected. For example, themonitoring means may include a splice detector adapted to monitor for astep in the thickness of the web, or to monitor for a step-change in thelight-transmissivity properties of the web. Other defects may bemonitored using a video camera looking at the surface of the web, forimperfections in that surface. The output of the monitoring means isprovided to the control means and which then appropriately operates thetab applicator including the in-line printer, to ensure the correctlyidentified tab is applied at the correct location.

By way of example only, one specific embodiment of this invention willnow be described in detail, reference being made to the accompanyingdrawings in which:—

FIG. 1 diagrammatically illustrates the embodiment of marking system;

FIG. 2 is a diagrammatic side view of the tab applicator used in themarking system of FIG. 1;

FIG. 3 illustrates the application of a tab to an advancing web; and

FIG. 4 is a simplified flow chart of the processing for marking a web ata noted defect.

Referring initially to FIG. 1, the marking system for a web 10, forexample of paper, being advanced along a path A includes a scanningvideo camera 11 looking at the upper surface of the web and producing anoutput signal 12 to a control arrangement 13. A splice detector 14 hastwo opposed arms arranged one each side of the edge margin of the web 10and monitors the transmissivity of the web; in the event that a splicepasses through the detector 14, the transmissivity is briefly muchreduced and a corresponding signal 15 is sent to the control arrangement13.

The speed of advancement of the web 10 is monitored by a speed sensingwheel 16 carried by an arm 17 so as to bear on the web, in opposition toa guide roller 18. The speed sensing wheel 16 provides to the controlarrangement 13 a pulsed signal the frequency of which depends upon thespeed of advancement of the web.

The control arrangement 13 analyses the signals 12 and 15 respectivelyfrom the video camera 11 and the splice detector 14, to determinewhether a mark need be applied to the web. If so, and in a timedrelation to the advancement of the web using the signal from the speedsensing wheel 16, an appropriate drive signal 19 is sent to a tabapplicator 20, downstream of the speed sensing wheel 16.

The tab applicator 20 is shown in more detail in FIG. 2. A series oftabs 22, each in the form of a self-adhesive label carried on a web ofbacking paper 23 is drawn from a reel 24 and guided around roller 25 toa labelling head 26 from which tabs 22 are dispensed one at a time, asthe backing paper is bent round a stripping beak 27. The backing paper,on being stripped of the tabs 22, is guided to a rewinding reel 28, forsubsequent disposal. Each tab, on leaving the backing paper, iscollected by a vacuum foot 29, ready for dispensing on to the web 10 atthe appropriate moment, in response to a signal from the controlarrangement 13. That signal causes the vacuum to be released from foot29 and instead to supply air under pressure to the foot 29, so jets ofair issue therefrom to blow the tab towards the web. Disposed adjacentthe vacuum foot 29 is an air jet head 30, which directs jets 31 of airon to the upper surface of a tab released from the vacuum foot 29, asthe tab follows path H, to thrust the released tab into engagement withthe advancing web, as shown in FIG. 3.

The tab applicator includes an in-line printer 33, disposed between theroller 25 and the stripping beak 27, to print on to the next tab to beprojected an appropriate marking or indicia, for the nature of thedefect noted by the video camera 11 or the splice detector 14.Typically, the in-line printer may print a group of three adjacentalphanumeric characters which will give sufficient flexibility to note awide range of defects. Though various forms of in-line printer may beemployed, preferably the printer is a direct thermal or a thermaltransfer printer, arranged to transfer ink from a thermal transferribbon to a plain-paper self-adhesive label.

As shown in FIG. 4, the control arrangement operates the tab applicatorin a timed relationship to the advancement of the web and controls theprinter, to print the required alphanumeric characters for the noteddefect. On recognising that a mark is to be applied to the web, andafter a calculated delay based on the output from the speed sensingwheel 16, the control arrangement 13 will drive the tab applicatorrelatively slowly to permit printing of the required marking on to thenext tab to issue from the applicator. The applicator continues toadvance the backing sheet until the printed tab has been received on tothe under-surface of the vacuum foot 29. At the required moment, havingregard to the advancement of the web, the vacuum is disconnected fromthe foot 29 and instead air under pressure is supplied thereto, soreleasing the tab from the vacuum foot 29 and blowing it along path H.The tab is thrust on to the web by further jets of air timed to issuefrom the air jet head 30. A tab applied in this way is shown at 34, inFIG. 1.

The control arrangement 13 includes a display panel 35 whichconveniently takes the form of a colour LCD touch display, to facilitatethe input of information by an operator. In addition, or separately, aremote control panel 36 may be provided, communicating through anumbilical cord to the control arrangement 13 or perhaps by an infra-redor wireless link. This permits the operator to make manual marks whererequired, or to change the output codes to be printed, dependent uponthe nature of a detected defect.

1. A marking system for a web advancing along a path, comprising: amonitoring station at which the web advancing along said path isobserved; mark signal means arranged to produce an appropriate marksignal on detection of a location to be marked and the nature of therequired mark; a tab applicator disposed downstream of the monitoringstation and arranged to apply an adhesive tab to the web at the detectedlocation, the tab inserter including an on-line printer for printingindicia on to each tab before the tab is applied to the web; and controlmeans receiving the mark signal from the mark signal means and drivingthe on-line printer and the tab applicator in a timed relationship tothe advancement of the web whereby each tab is positioned at thedetected location and carries appropriate indicia for that location. 2.A marking system as claimed in claim 1, wherein the tab applicatorincludes a labeling head adapted to apply tabs each in the form of aself-adhesive label to the web.
 3. A marking system as claimed in claim2, wherein the labelling head is provided with a vacuum foot whichcollects a printed tab and holds the tab until the detected location tobe marked is therebelow.
 4. A marking system as claimed in claim 2,wherein the labelling head includes at least one air-jet nozzle airissuing from which serves to thrust a tab discharged from the labellinghead on to the web.
 5. A marking system as claimed in claim 4, whereinan air controller is provided to cause air to issue from the at leastone air jet nozzle only when a tab is released from the vacuum foot, tobe applied to the web.
 6. A marking system as claimed in claim 1,wherein the on-line printer comprises one of a dot-matrix print-head, athermal print head or a thermal transfer print head.
 7. A marking systemas claimed in claim 1, wherein the tab applicator is arranged to advancethe next tab to be applied initially at a low speed while printing takesplace, the tab applicator then applying the printed tab at a relativelyhigh speed to the advancing web, at the detected location.
 8. A markingsystem as claimed in claim 7, wherein each tab is applied to theadvancing web in a direction generally transverse to the direction ofadvancement of the web.
 9. A marking system as claimed in claim 1,wherein each tab is applied to the web so that a part of the applied taboverhangs an edge of the web.
 10. A marking system as claimed in claim1, wherein monitoring means is provided at the monitoring station, saidmonitoring means comprising at least one of a splice detector and a webfault detector.
 11. A marking system as claimed in claim 10, wherein theweb fault detector includes a video camera arranged to scan the webadvancing along the path and a camera output is analysed to determinethe presence of one or more web defects.
 12. A marking system as claimedin claim 1, wherein the control means includes a remote operationcontroller permitting the manual production of a mark signal on visualdetection of a location to be marked.
 13. A method of marking a webadvancing along a path, which method comprises: monitoring the web as itpasses through a monitoring station provided on said path and producinga mark signal on detection of a location on the web to be marked, themark signal including information about the nature of the required mark;feeding the mark signal to control means which provides a drive signalfor an on-line printer and a tab applicator provided downstream of themonitoring station, the drive signal being provided in a timedrelationship to the advancement of the web; and using the drive signalto print an adhesive tab with the on-line printer so that the tabcarries appropriate indicia for the required mark and thereafterapplying the tab to the web, whereby each applied tab is positioned atthe noted location and carries appropriate indicia for that location.14. A method as claimed in claim 13, wherein the speed of advancement ofthe web is monitored and a speed signal produced dependant thereon, andsaid speed signal is supplied to the control means so that the tab maybe applied to the web at the required location.
 15. A method as claimedin claim 13, wherein the indicia printed on a tab comprise a group ofalphanumeric characters coded having regard to the noted defect to bemarked.
 16. A method as claimed in claim 15, wherein a group of threealphanumeric characters is printed on each tab.
 17. A method as claimedin claim 13, wherein each tab is applied in a direction transverse tothe direction of advancement of the web.
 18. A method as claimed inclaim 17, wherein each tab is applied to the advancing web so that apart of the tab overhangs an edge of the web.